There are some exceptions for auxliliary and modal verbs, but the endings for the different tenses are the following:
1.) present tense: -e, -(e)st. -(e)t, -en, -et, -en.
2.) past tense regular (weak) verbs: -e, -est, -et, -en, -et, en
3.) past tense strong verbs: -, -st, -, -en, -t, -en, -t, -en
For present perfect and past perfect you only need the present resp. past tense of "haben" or "sein", combined with the past participle of the main verb, for future tense you need the present form of "werden" plus infinitive, for future perfect the present perfect of "werden" plus infinitive.
You have to learn the tables for the auxiliary verbs "sein" and "haben" (as well as the modal verbs) sepratately. there are some itrregularities with the 2nd and 3rd person singular in the present of some verbs, but those do not concern the ending, but a change of stem vowel.

Hi!
German verbs that have irregular forms are also called strong verbs. Weak (regular) verbs follow the "standard" pattern.
BUT... There are also mixed verbs that combine elements of weak and strong verbs. (Quite how one might not follow the standard pattern, and yet not be classed as irregular eludes me.)
Apparently, denken is mixed.... but while denken is irregular in the past indicative and past conjunctive, rennen (i think) is only irregular in the past... so that makes it less mixed by my reckoning...
Anything irregular has to be memorised, so by the time you've done that, i don't suppose it helps much to know whether it's a strong verb or not... Weak Nouns, on the other hand are another matter... I love it when i remember them